The present invention relates generally to fluid ingress into an electric vehicle battery enclosure, and more particularly to a fill port access system permitting efficient application of water inside the enclosure in order to control any excessive thermal condition of the individual battery cells and modules.
Battery packs used with electric vehicles store large amounts of energy in a small space, producing high energy densities. These battery packs include an external housing that is designed for more than just environmental protection and packaging efficiency. The housing also enhances safety and stability, particularly under a range of anticipated abnormal operating conditions.
The battery packs are designed to provide high levels of safety and stability, yet situations can arise where a portion of a battery pack experiences a “short-circuit” condition which releases energy as heat. This short-circuit can occur from failure of a battery cell or from mechanical damage, such as a collision that damages an internal arrangement of cells of the battery pack.
The heat released from the short-circuit can be great enough, depending upon many factors including an amount of energy being converted and location of the short-circuit, to initiate a chain reaction. The chain reaction results from a heating of adjacent cells, which can cause them to overheat and fail, releasing heat that, in turn, propagates throughout the battery pack.
Once the reaction starts, it can continue to spread throughout the battery pack or a portion thereof until overheating cells are sufficiently cooled or the entire battery pack or the portion is consumed. A typical battery pack has a high thermal mass, mostly due to the mass of the cells. A failure of an individual cell provides for a relatively low energy release. Also, surrounding battery cells must be heated to as much as 200° C. or higher before they in turn release energy. These three factors mean that a full reaction that consumes all the cells of a battery pack may take anywhere from tens of minutes to many hours.
A conventional solution for a problem of an initiated chain reaction is to simply permit, once passengers and bystanders are clear of the vehicle, the reaction is allowed to run its course. While this situation is rare and designs are implemented to continue to make such situations ever more unlikely, there are some situations where it may be advantageous to terminate the reaction early (particularly to terminate additional heat release at will).
There are several factors that add to the challenges of early termination of such a reaction. One of these factors is the external housing. The housing has been engineered to resist structural corruption, by venting internally generated gases and resisting damage to the housing integrity from mechanical impacts/damage. The housing also provides environmental protection from water/moisture ingress. To do this, the housing is particularly engineered as a sealed, strong, metallic or fiber-reinforced polymer enclosure. To mitigate/extinguish an internal short-circuit reaction by application of any externality (e.g., water or heat-removing agents) directly to the outside of the housing is largely ineffective because the housing prevents the externality from direct contact with the cells.
It is further difficult to control the chain reaction because oxygen is released from some battery cathode materials during these reactions making it difficult to control the reaction by removing oxygen. The most effective way to control/limit potential and actual multiple-cell thermal runaway scenarios is to remove excess heat inducing reactions in other cells and, because of the large thermal mass, the best way to remove heat is for there to be direct contact between the affected cells and the heat-removing agent.
Issues surrounding the internal layout of the battery cells, protecting against accidental electrical energy release, ensuring safety from hot gas exhaust, and properly locating any solution within an electric vehicle form factor (among other considerations) make it a challenge to produce an acceptable solution.
The incorporated patent application referenced herein describes an effective and efficient solution for providing coolant agent ingress of a high energy density battery enclosure during an internal thermal event. Preferred embodiments of those solutions include use of a special fill port manufactured into an enclosure, among other elements. The solution could be improved in at least two situations: 1) enclosures manufactured without the special fill port and/or 2) enclosures wherein the fill port is unavailable in a specific instance (e.g., an orientation of the vehicle).
What is needed is an apparatus and method for providing coolant agent ingress of a high energy density battery enclosure during an internal thermal event for situations in which a special fill port is unavailable.